Various types of software data, such as music or other audio data, movies or other image data, game programs, and various types of application programs (hereinafter collectively referred to as content) may be stored in a recording medium including a disk-type information recording medium (medium) such as a Blu-ray (registered trademark) disc and a digital versatile disc (DVD), and an information recording medium (medium) such as a flash memory.
A content storage medium is attached to a reproduction device such as a personal computer (PC) and a player possessed by a user for reproduction of content, for example.
Currently, a large number of information recording media (media) store high-definition (HD) images. A reproduction device reproduces HD images from the information recording media (media).
In recent years, the use of information recording media (media) recording ultra high definition (UHD) images, such as 4K content and 8K content, is increasing.
It is estimated that parallel use of HD image content and UHD image content continues for a while.
The HD content and the UHD content are different in their coding (codec) modes, for example. Accordingly, for reproducing and displaying UHD images, a reproduction device handling UHD and a display handling UHD need to be equipped based on the necessity of a UHD content reproduction environment different from a HD content reproduction environment.
A number of reproduction devices, displays, and other user devices widely used at present are devices handling only HD content. The number of user devices (reproduction devices and displays) capable of handling UHD content is still small. Accordingly, it is expected that content providing companies create both HD content and UHD content for identical movie content, and supply to users both information recording media such as disks for storing HD content, and information recording media such as disks for storing UHD content, for example.
On the other hand, a reproduction device in this situation needs to perform different processes for reading content from a disk storing HD content (disk of version 1) and executing reproduction, and for reading content from a disk storing UHD content (disk of version 2) and executing reproduction.
More specifically, for reproduction of HD content read from a disk storing HD content (disk of version 1), for example, the reproduction device needs to perform a decoding process adopting codec (decoding function) corresponding to the encoding mode of the HD content.
On the other hand, for reproduction of UHD content read from a disk storing UHD content (disk of version 2), the reproduction device needs to perform a decoding process adopting codec (decoding function) corresponding to the encoding mode of the UHD content.
Even for content reproduction achieved by processes other than these decoding processes, processing peculiar to respective disks of corresponding versions needs to be performed for accurate content reproduction.
Accordingly, the reproduction device initially checks the version of the disk attached to the reproduction device, and performs a reproduction process by utilizing a reproduction environment corresponding to the version.
However, a problem occurs in controlling execution of a disc-unbound application which may be utilized in a content reproduction process including disk switching.
In case of a long film, for example, movie content may be divided into two or more parts and recorded into the corresponding number of disks. For example, a disk 1 storing a first part of the movie content, and a disk 2 storing a second part of the movie content may be provided for a user. In this case, the user initially attaches the disk 1 to the reproduction device to execute a reproduction process. After completion of reproduction of storage content (first part) of the disk 1, the user removes the disk 1 and attaches the disk 2 to reproduce storage content (second part) of the disk 2.
The foregoing disc-unbound application is an application stored in the disk 1, for example. The disc-unbound application is read from the disk 1, and loaded into a RAM or the like of the reproduction device to be executed. This application is continuously executed even after removal of the disk 1 from the reproduction device to be executed after a reproduction start of the disk 2.
In other words, this application is an application executable by the reproduction device even during disk switching and after disk removal.
An application continuously executed even after removal of a disk from a reproduction device and attachment of another disk to the reproduction device, i.e., an application executable regardless of the presence or absence of disk attachment is referred to as a disc-unbound application. On the other hand, an application executed only in an attachment state of a particular disk is referred to as a disc-bound application.
These applications are described in PTL 1 (Japanese Patent No. 4919431), for example.
A disc-unbound application of a specific example outputs a message for instructing a user to switch a disk, and executes a BGM reproduction process or like processes.
For example, a disc-unbound application of this type displays a message for instructing disk switching at the time of completion of content reproduction of the disk 1, and executes BGM reproduction or advertisement content reproduction until completion of attachment of the disk 2 and a start of content reproduction of the disk 2.
In this case, however, such a situation may occur, for example, that a user erroneously attaches a disk of a version (disk of version 2 storing UHD content) different from the version of the reproduction completed disk (such as disk of version 1 storing HD content) at the time of disk switching.
In this case, the user may reproduce low image quality content different from image quality intended by the user, or cause reproduction errors without recognizing attachment of the disk of the different version, when the foregoing disc-unbound application is continuously executed.